Car body roll dampening spring bolster

ABSTRACT

An arrangement for controlling roll in high capacity railroad freight cars when loaded, while providing a soft car protecting ride when the car is empty, in which a dampening type volute spring is incorporated in the truck spring groups that support the respective truck bolsters, with the volute spring having a trap free height that is less than the height range that the bolster rids in when the car is empty, but is greater than the height range that the bolster rides in (including possible roll) when loaded. This permits the absorption potential of the roll controlling volute springs to be independent of the bolster empty riding height, which makes available for roll control purposes full utilization of the usable absorption potential that can be built into a volute spring of this type.

United States Patent Wulfi Sept. 4, 1973 CAR BODY ROLL DAMPENING SPRINGPrimary ExaminerGerald M. Forlenza BOLSTER Assistant Examiner-HowardBeltran Inventor: Cal w. Elmhurst, In. Att0rney-Mann, Brown, Mcwllliams& Bradway [73] Assignee: Holland Company, Lombard, Ill. [22] Filed: Mar.5, 1971 [57] ABSTRACT An arran ement for controllin roll in hi h ca acit21 A 1.N.:121258 g g g p y 1 PP o railroad freight cars when loaded,while providing a soft car protecting ride when the car is empty, inwhich [52] U.S. Cl. 105/197 D, 267/4 a dampening type volute spring isincorporated in the B61f 1361f truck spring groups that support therespective truck [58] Field of Search 105/197 R, 197 D, bolsters, withthe volute spring having a trap free height 105/197 DB, 197 DP; 188/33;267/3, 4 that is less than the height range that the bolster rids inwhen the car is empty, but is greater than the height [56] ReferencesCited range that the bolster rides in (including possible roll) U ITSTATES PATENTS when loaded This permits the absorption potential of930,630 M933 symington t 105,197 R X the roll controlling volute springsto be independent of 2,065,992 12/1936 Barrett 105 197 DP the bolsterempty rldmg height, whlch makes avallable 2,105,651 1/1938 1161mm 267/4for control P p full utilization of the usable 2,571,519 10/1951 Barber105/197 DB absorption potential that can be built into a volute2,587,315 2/1952 Haynes 105/197 DB spring of this type. 2,649,298 8/1953Wulff et a1 267/62 5 Claims, 16 Drawing Figures U N ITS 0F ABSORPTIONPATENIEDB 4 i973 3.755.162

MEI"! 0F 7 {F X Y SPRING GROUP HEIGHT IN INCHES W 1 INVENTOR CAL W WULFFATT 'YS.

CAR BODY ROLL DAMPENING SPRING BOLSTER This invention relates to amethod and apparatus for controlling body roll in high capacity railroadcars, and more particularly, to a method and apparatus for controllingroll in high capacity cars when loaded that provides for a soft ride forthe car when empty.

Certain kinds of freight cars, as, for instance, hopper cars, gondolacars, tank cars and the like, usually run under either full load orempty load conditions. Single purpose trains are an outgrowth of thiseconomic fact, and typical of such trains are coal, potash and oretrains as well as trains carrying bulk liquids or gases in tank cars.

There have been attempts over the years to increase the capacity offreight cars of this type so that today, 100 ton cars are commonplace.As such cars have gone up in capacity and carry larger loads, the centerof gravity of the cars as loaded has moved upwardly, and, of course, thegreater mass and higher center of gravity combine to accentuate thetendency of the car to rock or sway about its longitudinal axis as itmoves along the track, when such factors as the truck and rail jointspacing, speed of movement, and basic spring rates of the truck springgroups are taken into consideration and with the end result being wheellift and in many cases actual derailment.

Numerous ways have been devised for attempting to control the rollproblem of these high capacity cars. For instance, hydraulic dampingdevices have been included in the spring groups interposed between thetruck bolster and the truck frame, but this type of solution has fallenshort of its mark. One successful way to control the roll problem thathas come into wide use has been to substitute for one or more of thecoil springs in the bolster spring group one or more volute springs ofthe type generally shown and described in Wulff et al. U.S. Pat. No.2,649,298, granted Aug. 18, 1953. This volute spring is of the dampeningtype and has a special arrangement characterized by having a helix anglethat increases upwardly from the outer active coil to the inner activecoil, and has an as-coiled" pitch which increases from the outer activecoil to the inner active coil (sometimes referred to as reverse pitch),with the result that as the spring is compressed, controlled frictionforces are developed between the adjacent coils, whereby the springserves as an energy absorber of the dissipative type.

In considering springs of this type there are several terms of art thatneed to be kept in mind, and these are as follows:

A critical dimension of a spring of this type is its socalled trap freeheight," which is the equilibrium position that the spring assumes onrelease, that is, the equilibrium between the spring design load orstrength on release and friction resistance forces acting due to theradially compressed coils of the volute.

Stated in other words, the trap free height of a volute spring made withreverse pitch, in accordance with the said Wulff et al. U.S. Pat. No.2,649,298, is the point of equilibrium between the friction forces dueto the radial compression of the coils and the stresses in the volutespring which are tending to extend the length of the spring. Any timethat the spring is compressed, the radial friction forces betweenadjacent coils is increased, and upon release the spring will return toa given height, called trap free height, when equilibrium is establishedbetween the radial friction forces and the forces tending to extend thespring.

It is a phenomenon of a spring of this type that when such a spring isat its trap free height it can be extended in length by inflicting itwith hammer blows, which have the effect of vibrating the coils and sodisturbing the face-to-face frictional contact as to permit the springto further extend. A spring that is properly designed, when given one ormore hammer blows of unit force, will on each blow elongate to a new andlonger dimension up to an asymptotic relation; this is called therap-out length of the volute and the rapout length for productionpurposes may be different than it is for fatigue testing purposes. Theunit. force for each hammer blow required to effect extension of thevolute spring under rap-out conditions depends upon the inherent designof the particular volute, including the extent of the reverse pitch,distribution of metal within the coils, chemical composition, etc.

With certain volute springs of reverse pitch, made in accordance withWulff et al. U.S. Pat. No. 2,649,298, the radial friction forces thatare present may be such that, when the spring is given a sharp blow oflarger unit force, it may extend beyond its rap-out height to what iscalled jump-out height, which merely means that the vibration on thespring due to the blow so releases the frictional forces as to cause thespring to extend suddenly to or perhaps even beyond (due to momentumestablished by sudden release) its design-free height or length.

The design-free height of a volute spring is the height that the springwould have if there were no friction between coils. The asymptote of therap-out height for all practically purposes may be considered thedesign-free height, and even the jump-out height is approximately thesame as the design-free height, except that with jump-out the momentumof the coil extension with the subsequent action of friction betweencoils may hold the coil in an extended position somewhat abovedesign-free height.

My studies of the problem of how to minimize body roll or sway in highcapacity cars have revealed that little, if any, attention has been paidto the fact that such cars ordinarily run either fully loaded or empty.In recent years the problems experienced with fully loaded high capacitycars have been such that efforts to control the roll problem have beenconcentrated on the action in transit of such cars under loadedconditions. As a result, too much attention has been given to full loadcondition and almost no attention to empty load conditions. Experiencehas shown that significant car damage has been occurring while the carsare traveling empty such as wear, metal fatigue and derailment due toexcessive rocking. This has suggested to me that any suspensionsystemwhich might effectively deal with the car fully loaded may not beappropriate to the running of such car under empty load conditions.

It is therefore a principal object of this invention to provide asuspension system for railroad cars which protects the car for bothfully loaded operation and empty load running conditions.

Another important object of the invention is to provide a spring groupfor supporting the truck bolster on the truck frame which ischaracterized by the fact that at the loaded car running height of thebolster, volute roll control absorbers operate to effectively controlbody roll, and at the bolster empty car running height,

only such snubbing effect as is required to control pure verticalmovement is operative.

Heretofore, springs of the type disclosed in said Wulff et al. patenthave been used in spring groups for roll control purposes in which thespring trap free height has been equal to or greater than the empty carbolster riding height. One of the difficulties which has beenexperienced in making this type of roll control device is that each heatof steel" (i.e., the particular batch of metal from which the volutesare made) has to be tested to be sure that such volutes will have a specific minimum energy absorption under specified fatigue testingconditions. It has been found that in practice a very fine balance hasexisted between such trap free height and absorption requirements, withthe result that frequently numerous costly trials have had to be run,with variations being made in the spring specifications relative tocoiling roll pressure, heat treatment, and the like, for a particularheat, before that particular heat can be approved for manufacturingpurposes.

It is therefore another principal object of this invention to provide aroll control volute spring in which the absorption potential is freedfrom the empty car riding height limitation so that the volute springcan be arranged to achieve full utilization of the usable absorptionpotential of which its particular heat of steel is capable.

Other objects of the invention include: to provide in conjunction with aride stablized bolster of a freight car, a spring group for supportingthe bolster which is characterized by having a relatively low springrate for providing a smooth ride when the car is running empty and withsubstantially no roll control needed or provided under those conditions,but when the car is running fully loaded, the spring group provides fullcontrol over body roll; to provide means for supporting one or more rollcontrol volute springs in a group in such a manner that the volutespring or springs are inactive under empty car running conditions; toprovide roll control volute springs arranged for full utilization oftheir usable energy absorption or dampening potential of which each heatof steel from which such springs are made is capable; and to providearoll control arrangement that is economical of manufacture, that isreadily installed, that permits marked savings in time and money intesting for heat approval purposes, and is readily applicable tostandard truck designs, and is long lived in operation.

A further and subsidiary object of the invention is to incorporate oneor more volute springs of reverse pitch type into a spring group of acar truck in such a manner that not only is the trap free height of thevolute spring below the lower amplitude of bolster height for empty caroperation, but also to operate the volute spring on that portion of itsload deflection curve which has substantially constant spring ratecharacteristics. In the past, where the trap free height of the volutespring in the group has been at or above bolster empty load height, orstatic empty load condition, the volute spring, when operating underfully loaded car conditions, and when resisting roll, has under maximumroll conditions operated in part on that portion of its load deflectioncurve which has increasing rate, and has therefore had a tendency totransmit roll forces into the car truck rather than absorb them. This isnot in itself a serious objection and may be employed in practicing thebasic aspects of this invention, but there are circumstances in which itis more desirable to utilize the roll control volute spring only in thearea of its load deflection curve where it exhibits constant rate.

In accordance with this invention, there is provided for supporting thetruck bolster on its side frames a spring group arrangement thatincludes a plurality of the usual bolster helical springs, and with thevertical motion of the bolster being dampened in any suitable manner, asby employing one of the conventional socalled built in controlarrangements, and at least one dampening type roll control volute springhaving a trap free height that is below the bolster empty car ridingheight (including its amplitude of movement at that height), and that isabove the bolster loaded car running height sufficiently to accommodateroll amplitudes. In other words, the roll control volute spring isnormally not functional during any phase of light car operation, butalways functional during loaded car operation. In this connection, thespring group helical springs, to the exclusion of the roll controlvolute springs, provide the softer ride that is desirable for the carwhen empty, while when the car is loaded, the roll control springs, inaddition to supplementing the load supporting function of the helicalsprings of the group, insure roll control at critical speeds whichproduce roll. As the trap free height criteria of the roll controlvolute springs is not equated to empty car bolster height, the volutesprings may be designed to better attain desired utilization of theusable absorption potential of which the particular heat of steelinvolved is capable for improved roll control.

Other objects, uses and advantages will be obvious or become apparent asthe disclosure proceeds and the description is read in conjunction withthe accompanying drawings, in which like reference numerals indicatelike parts throughout the several views.

In the drawings:

FIG. 1 is a diagrammatic end view of a high capacity railroad carshowing the body and major components of the truck in largely blockdiagram form, and illustrating the basic nature of the instantinvention;

FIG. 2 is an end elevational view of a spring group arranged inaccordance with this invention interposed between one end of a ridestabilized bolster and truck side frame of a standard make, with thebolster shown at its empty load height;

FIG. 3 is a diagrammatic plan view of the spring group of FIG. 2,illustrating the positioning arrangement of the elements making up thisspring group;

FIG. 4 is a bottom plan view of a bolster for another standard make oftruck which has been modified in accordance with this invention;

FIG. 5 is a sectional view through the bolster end shown in FIG. 4,taken substantially along line 55 of FIG. 4;

FIG. 6 is a view similar to that of FIG. 2 illustrating the bolster ofFIGS. 4 and 5 applied to its truck side frame with the spring group ofFIG. 3 interposed therebetween;

FIG. 7 is an enlargement of the volute spring and associated parts shownin FIG. 2;

FIG. 8 is a plan view of the volute spring, with its dead coils beingindicated by distinctive crosshatching;

FIGS. 9, l0 and 11 are graphs illustrating the manner in which thisinvention acts in operation;

FIG. 12 is a curve illustrating the relation between roll control volutetrap free height, design free height and rap-out height in devices ofthe type to which the invention relates;

FIG. 13 is a graph similar to that of FIG. 9, but for a modified form ofthe invention;

FIG. 14 is a graph illustrating the manner in which the modified form ofthe invention operates;

FIG. 15 is a fragmental view of the volute base of the embodiment ofFIGS. 13 and 14; and

FIG. 16 is a graph similar to that of FIG. 11 but illustrating thatabsorptive action of the volute of FIGS. 13

GENERAL DESCRIPTION Reference numeral 10 of FIG. 1 generally indicates arailroad car equipped with this invention. Car 10 includes the usualbody 12, including underframe l4 applied in the usual manner adjacenteach end thereof to bolster 16 of the individual car trucks 18 (thoughonly one truck is shown), which bolster 16 at its ends 18 and 20 restson spring groups 22 and 24 that are in turn sup ported by the truck sideframes 26 and 28 which are journaled in the usual manner on truck axles30 riding on wheels 32 which engage the usual track rails 34.

The body 12 illustrated is largely in block diagram form and is intendedto represent the various types of high capacity car bodies that arecommonly employed today in 100 ton cars and the like.

The single truck 18 that is illustrated is only diagrammatically shownto bring out the principal novel features of same for illustrativepurposes, it being understood that the truck 18 is intended to representany commercial railroad car ride stabilized truck equipped with abolster 16 or its equivalent for supporting car body 12, either at thecenter plate structure 36, or at the side bearings 38, or both.

As is well known in the art, the function of the spring groupings 22 and24 is to resiliently support the body 12 so that it has a smooth ride.I-Ieretofore, it has been the practice to form the spring groupings 22and 24 by inserting a number of helical springs such as springs 40 and42, or springs 40 alone, between spring seats 44 and 46 defined by thebolster and side frames, respectively, with the number and size ofsprings employed depending on the load to be carried. In more recentyears, this has been accompanied by snubber devices of various types tocontrol the vertical movement of the bolster. The volute spring of thesaid Wulff et al. patent is an example of one type of ride stabilizationdevice, it being arranged to take the place of one or more of thesprings 40 in the spring group and be interposed between and directlybear against the bolster and side frame spring seats for ridestabilization purposes. Another familiar form of snubbing deviceinvolves friction shoes carried by the bolster that are spring biasedagainst hardened friction surfaces applied to the side frame columns.

In any event, the function of such snubbing devices is to provide ridestabilization for the bolster in the sense that pure vertical movement,as distinguished from rocking or rolling motion, will be controlled.

In this connection, it is pointed out that, in practice, the springgroups 22 and 24 are designed to support the bolster l6 and the load itcarries at a predetermined elevation relative to the track rails 34,which may be spoken of in terms of positioning the spring seats 44 ofthe bolster a specified distance above the spring seats 46 of the sideframes. For instance, considering the matter in these terms, the bolster16 when car body 12 is riding empty will be riding at a riding height orlevel 48 (see FIG. 1), while when loaded to rated capacity, bolster 16will be riding at a lower riding height or level 50 (it being assumedthat levels 48 and 50 are horizontally aligned with the bolster springseats 44). The height involved in such terms as trap free height anddesign free height that have already been defined means a distancemeasured from the same point of reference as bolster riding height.

More recently, high capacity railroad cars have come into wide use whichhave, by virtue of the higher center of gravity and heavier loadsinvolved, made critical the problem of body roll insofar as highcapacity equipment is concerned.

Car body roll is caused by a number of factors, including location ofcenter of gravity, weight being carried, truck and rail joint spacing,speed of movement and basic spring rates of the resilient supports forthe car body. The problem is particularly acute in connection with 100ton hopper cars when loaded, though experience has shown that any fullyloaded car of 100 tons and up moving at speeds of 15 17 mph. that passesover three low rail joints in a row will develop a severe tendency toroll with significant likelihood of derailment.

Efforts to overcome the roll problem have been centered on controllingin some suitable manner the motion of the bolster under fully loadedconditions. One roll preventing arrangement that has been highlysuccessful in providing full control over roll in high capacity carswhen loaded has involved the replacement of one or more standard helicalsprings of each spring group with a corresponding number of volutesprings of the type disclosed in said Wulff et al. patent that arespecifically designed for roll control purposes in addition to providingresilient support for the load and have a trap free height that isintended to be at least equal to or greater than the bolster empty loadriding height.

However, as stated heretofore, the emphasis has been on ride control forloaded condition, with little or no attention being paid to empty carride.

In accordance with this invention, the spring groups 22 and 24 arearranged to provide a sufficiently cushioned ride for the body 12 whileempty, while yet provide adequate roll control for the body when loaded.More specifically, the spring groups 22 and 24 are arranged so that whenthe truck bolster 16 is riding at the empty car level 48, the rollcontrol devices that are included are inoperative and car body 12 issupported solely by the helical springs 40 and 42 (suitably snubbed forvertical movement control), which provide a comparatively soft ride forthe car body when empty. However, when the car body 12 is loaded, theroll control devices are rendered fully operative to control body rollthrough its normal anticipated amplitude and also contribute to theresilient load support provide by the spring group.

In terms of specifics, reference may be had to FIG. 9, which is a graphillustrating the results of a specific application of the principalinvolved, and plots roll control volute spring assembly height in inchesagainst load in thousand pound units for a volute roll absorbing springof the type shown in said Wulff et al. patent that is designed for tonhopper car use, in which compression and release curves 60 and 62 showthe action of a conventionally designed volute spring of this type oncompression and release, while compression and release curves 64 and 66show the corresponding curves for a volute spring made in accordancewith this invention. Curve 65 is the dynamic curve showing the designcharacteristics of the volute springs when considered purely as loadsupporting springs, as distinguished from energy absorbers.

As indicated in FIG. 9, it is assumed for purposes of disclosure thatthe bolster empty car riding height will be about 9 isths inches with abolster vertical movement amplitude ranging from about 9 to about 9 7/8inches while the bolster loaded car riding height will be about 7 7/8thsinches with a maximum roll amplitude of about 2 inches, varying fromabout 7 to 9 inches in riding height (though it should be understoodthat these dimensions in practice will depend on a number of factorsincluding type of car involved, spring rate character of the springgroups employed, etc).

Heretofore, damping type volute roll absorbers of the type shown in saidWulff patent have been designed with the intention that they maintaincontact with the bolster throughout its entire range of movement (forconvenience these roll absorbers are termed, for purposes of thisdisclosure, constant bolster contact absorbers or roll control devices);it will be observed from FIG. 9 that the release curve 62 for theconventional constant contact volute roll absorber indicates a trap freeheight that is substantially equal to the empty car riding height of thebolster. In accordance with the instant invention, the trap free heightof the volute roll absorber is substantially less than the empty carriding height (including amplitude of movement X at empty loadconditions), but exceeds the loaded car roll amplitude, as indicated atY in FIG. 9, wherein the release curve 66 indicates that the volute rollabsorber of the present invention will have a trap free height of about9 /4 inches. The dynamic curve (which neglects energy absorption) forthe improved roll absorber will follow curve 65.

It is also an important feature of the invention that the roll controldevice employed be arranged to stay in place when the car is empty in amanner that will avoid having to make significant modifications ineither the bolster or the side frame.

A specific application of the invention is shown in FIGS. 2, 3 and 7wherein the spring group 70 is shown interposed between the spring seat44A of bolster 16A and spring seat 46A of side frame 71 that is part ofa Barber S-2-C stabilized truck 75 of well known design having a snubbedbolster 16A.

Spring group 70, as indicated in FIG. 3, is of the nine position type inwhich the outer left and inner right spring positions are occupied byvolute roll absorber devices or units 72 arranged in accordance with thepresent invention, the other positions being occupied by the respectivesprings 40 and 42, though it is to be understood that functionally, thedevices 72 could be located at any position in the group (assuming thebolster and side frames permit this).

The volute roll absorber devices 72 each comprise a volute spring 73 ofthe type disclosed in said Wulff et al. patent, but having its trap freeheight such that when the bolster is riding at the empty load level, asshown in FIG. 2, the upper end 74 of the volute spring is spaced fromthe bolster spring seat 44A for all amplitude of movement of the bolsterunder empty load conditions. Retainer spring 77 applied between spring73 and the bolster resiliently holds unit 72 from displacement withouthaving to significantly modify the truck parts involved.

In the embodiment of FIGS. 4 6, the invention is shown applied to an ASPRide Control Truck 76 in which the bolster 16B is an A-3 Ride Controlbolster, both made and sold by American Steel Foundries.

In trucks of the type shown in FIGS. 4 6, the bolsters conventionallyinclude spring retainer flanges. For purposes of this invention, thespring retainer flanges at the outer left and inner right group springpositions are removed from the bolster, and bosses 82 are applied oncenter in these positions, as indicated in FIG. 4, to receive theretainer spring 77. Spring retainer flanges are present to permitalternate use of a conventional spring group, using the same bolster anda conventional roll absorber of different make located at the outerright and inner left spring group positions. The bosses may be of eitherY" design (FIG. 4) or of circular design (FIG. 6) in cross-section. Inthe case of bolster 16A (FIGS. 2 and 7), the existing boss 83 in thesame position may be utilized and no flange deletion is necessary.

FIG. 1 is intended to diagrammatically illustrate both the specificembodiments of FIGS. 2 6 in showing volute spring unit 72 appliedbetween the bolster l6 and side frames 26 and 28 in the respectivespring groups 22 and 24, with the bolster 16 being shown in the emptyload car height bolster riding position (indicated by the line 48), andthe loaded car bolster riding position height being indicated by theline 50. FIGS. 1 6 are intended to illustrate application of theinvention to a 100 ton hopper car which will have 263,000 pounds maximumweight on rail when fully loaded. However, the invention is equallyapplicable to any railroad car requiring both roll control in the loadedcondition and a soft ride in the empty condition. Furthermore, the rollcontrol devices 72 may be at any desired position in the group that issuitably prepared, as in the manner indicated, to accommodate receptionof the units 72 therein.

In the embodiments of FIGS. 1 11, the trap free height relation of thisinvention is achieved by building into the devices 72 higher radialpressures that thus bring into fuller utilization the absorptionpotential that can be built into the volute. The degree to which theabsorption potential is to be utilized for any particular application is(in light of this invention) a matter of choice and design, but sincethe volute trap free height no longer must be equal to or greater thanthe empty load bolster riding height, the full absorption potential ofthe volute, insofar as it can be used for roll control purposes, is nowavailable to the designer.

The graphs of FIGS. 13 16 illustrate a roll control device 72A (FIG. 15)in which the prior art constant contact absorber represented by curves60 and 62 is shortened in length as required to have its trap freeheight at about 9 A: inches, rather than at the constant bolsterengaging height of 9 56 inches that is shown in FIG. 9. This not onlybrings into play the empty load riding benefits of this invention, butalso results in the volute operating along the straight line portions ofits deflection curves in controlling loaded car roll, as indicated bythe absorption envelope 85 of FIG. 14.

In FIG. 10, the dynamic action of a spring group arranged in accordancewith the showing of FIGS. 1 l1 and embodying volute roll control devices72 each having the improved characteristics indicated in FIG. 9 isplotted, assuming the spring group is applied to a 100 ton car having263,000 pounds maximum weight on the rail, with each spring group 70having a group spring rate of 26,000 pounds per inch with a solidcapacity of 112,546 pounds under dynamic conditions. The result is curve90, wherein it will be seen that the portion AB of the curve lies alongthe straight line 92 that represents the dynamic action of the sevencoil springs 40 and 42 (suitably snubbed as by employing built in typesnubbing devices for vertical movement control) alone from zero load tothe point where devices 72 are engaged, whereupon there is a break inthe curve and no bolster deflection until the load represented by pointC is reached, whereupon the curve portion CD is attained for furtherincreases in load up to near solid conditions.

In the showing of FIG. 11, application of the invention (in the form ofFIGS. 1 11) is illustrated in terms of units of energy absorptionplotted against spring group height in inches for a truck of the typeshown in FIGS. 4 6 equipped with the invention, in which line 94illustrates energy absorbed by the operation of built in snubberscontrolling the pure vertical motion of the bolster, curve 96illustrates the operation of volute roll absorber units of the prior arttype (which are in constant contact with the bolster), and curve 98represents the improvement provided by the instant invention (with theportions of curve 98 that are coincident with curve 94 being set offslightly to clearly distinguish all three curves). Experience hasindicated that roll control in 100 ton cars and the like requires thatthe roll control units have a damping factor of at least three to fourtimes that necessary for control of pure vertical bolster motion withminimum loss in resiliency, and in the application of the invention to a100 ton car, the energy absorption on deflection of the bolster from itsempty car riding elevation to engagement with the units 72 will followline 94 from maximum empty car riding height to the trap free height ofunits 72, whereupon the curve 98 will break and jump immediately to wellabove the level of curve 96 for full load ride control and roll control.The increased absorption that is indicated by curve 98, for loaded carride and roll control is achievable by reason of the increasedutilization of the absorption potential of the volute (in this case byincreased radial pressures being built into the volute coils) whichwould not be possible if the trap free height of the volute had toapproximate the bolster empty load height.

In the showings of FIGS. 9 l4, and 16, the amplitude of movement of thebolster in the empty load conditions is indicated by dimension X whilethe amplitude of movement of the bolster under loaded conditions,including roll amplitude, is indicated by dimension Y.

In the showing of FIG. 13, curves 60A, 62A and 65A correspond to curves60, 62 and 65 of FIG. 9, except that the roll control unit involved isshortened (by about one-half inch) to provide the trap free heightrelation contemplated by this invention, which results in curves 60A,62A and 65A being shifted to the right of corresponding curves 60, 62and 65 of FIG. 9.

FIG. 14 shows the dynamic action of a spring group arranged inaccordance with the showing of FIG. 3 and embodying roll control devices72A each having the improved characteristics indicated in FIG. 13,assuming the same loaded car conditions as in the case of FIG. 10. Thecurve 90A illustrates the dynamic action of the group (ignoring energyabsorption) of which the portion EF lies along straight line 92A thatrepresents the dynamic action of the seven coil springs 40 and 42(suitably snubbed, as previously indicated) alone from zero load to thepoint where devices 72A are engaged, whereupon there is a break in thecurve and no bolster deflection until the load represented at G isreached, whereupon the curve portion OH is attained for furtherincreases in load up to near solid conditions. The action of the units72A in controlling roll is thus along the straight line portions of thevolute calibration curves, as indicated by envelope 85.

The showing of FIG. 16 is of the same type as FIG. 1], curves 94 and 96being the same as curves 94 and 96 of FIG. 11, respectively and curve98A corresponding to curve 98 of FIG. 11.

Units 72A thus have the advantage of operating for roll control purposesentirely along the straight line portions of their deflection curves andat reduced stress levels, in addition to insuring the desired soft ridefor the car under empty load conditions. Device 72A thus provides anenergy absorbing action comparable to hydraulic roll control devices.

In all embodiments of the invention, it is to be understood that theroll control devices of this invention are arranged so that theirvolutes reach, on release, the trap free height relationship that hasbeen described and maintain approximately this trap free height whilethe car runs empty in spite of the normal vibrations and shocks that thevolutes will be subjected to in service. In other words, the voluteunits of this invention are so constructed that they will not move torap out height or length, much less design free height, under normalservice vibrations and shocks; but even if an excessive blow werereceived, the first compression of the spring would restore the desiredtrap free height.

The practice of the instant invention provides a number of importantbenefits. For instance, for empty car operation, the spring groupsprovide a 25 to 30 percent lower spring rate, all helical springsupport, for the bolster that is controlled by suitable snubbing devicesof the type indicated for optimum vertical movement only. This insuresmaximum riding spring cushioning action for the bolster and load carriedthereby, a minimum transferability of forces involved, a lower naturalfrequency for the spring system involved, and a somewhat lower center ofgravity as the bolster riding height will be lower since the loadsupport heretofore provided by the roll control devices will not bepresent under empty load conditions. Furthermore, tendencies to rockunder empty load conditions, which could not be controlled due to thestiffness of conventional spring groups, are cushioned and dissipated bythe helical springs of the groups 70 to the exclusion of devices 72 or72A.

For loaded car operation, roll control of the car body is assuredwithout affecting the dynamic riding height of the spring group.Furthermore, since the trap free height of the volute springs no longerhas to be an approximation of the empty car bolster riding height, theabsorption potential of the volute roll absorbers can be enhanced, ifdesired, up to the full usable potential of which each heat of steel iscapable, with the result that when the necessary relationships betweencar geometry, center of gravity and truck centers exist, a single volutedevice 72 may be employed where two prior art volute roll absorberdevices have formerly been employed (note FIG. 11).

Moreover, since fatigue test production control specifications can bemet without having to be concerned with the trap free heightapproximating the light car bolster riding height, approvals for eachheat of steel can be expedited and simplified.

SPECIFIC DESCRIPTION The specific nature of the truck bolsters and sideframes indicated in FIGS. 2, 4, and 6 are well known to the art, theBarber stabilized truck being shown at page 797 of the 21st Edition ofCar Builders Cyclopedia, and the Amsted ride control truck being shownat page 785 of the same publication. In the arrangement of FIG. 2, thecolumns 100 and 102 are provided with hardened friction surfaces 104 and106 against which the respective friction shoes 108 and 110 (carried bythe bolster 16A) are spring biased for snubbing purposes. The bolster16B and side frames 79 of the embodiment of FIG. 6 (only one side frameis shown) are similarly equipped as indicated by corresponding referencenumerals employing the suffix A.

The volute spring units 72 (see FIGS. 7 and 8) each comprise a volutespring 73 made in accordance with the said Wulff et al. patent andhaving a trap free height in accordance with the standards that havebeen here indicated, such that when the bolster is riding at its emptycar height, the upper end 74 will have the spacing below the bolsterspring seat that as indicated in FIG. 7. Spring 73 is wound to provide areverse pitch, negative helix in the as coiled condition; in otherwords, spring 73 has a negative helix angle and an increasing axialpitch, as defined by said Wulff et al. patent. In FIG. 8, the outer deadcoil is indicated at 122, the inner dead coil at 124, the outer activecoil at 126, the middle active coils at 128 and 130, and the inneractive coil at 132.

As previously indicated, the combination of steel chemistry, materialdistribution from coil to coil, and coiling roll pressure are the primefactors controlling absorption potential of the volute spring. For 100ton car applications, it is preferred that the spring 73 be fabricatedto provide minimum absorption (difference between compression andrelease loads) of 4,500 pounds at 6 l5/16ths volute height after 50,000cycles of compression and release for each of two trial snubbers foreach heat of steel, with 100,000 cycles minimum to spring failure.

The inner inactive coil 124 has received within same retainer cylinder134 through which extends stem 136 of bolt 138 having a head 140 whichis seated in recess 142 of the base disc 144 of the unit (see FIG. 7).The base disc 144 includes a hub portion 146 through which bolt 138extends, and on which rests the retainer 134.

Retainer 134 is secured in place by suitable nut 148 applied againstlock washer 150 seated against washer 153, which in turn is seatedagainst retainer cylinder 134.

As indicated in FIG. 7, the base disc 144 of the unit 72 rests againstthe spring seat area 46 of the side frame, and has its spring seatengaging surface 151 excised thereabout as at 152 to allow for lateraland roll motions of the bolsters.

The retainer spring 77 has one of its ends 154 received about thebolster boss 82 or 83 and the other of its ends 156 received about thenut 148 and against the washer which thus serves as a spring seat forthe spring end 156. Spring 77 is a comparatively light compression typespring of sufficient strength to hold unit 72 in place when spring 73 isseparated from the bolster.

The retention in place of spring 73 by spring 77 provides a simple butexpedient way to satisfy the need to insure that unit 72 is retained inits operating position when the car is running empty so that it does notrequire special attention each time the car is loaded. Moreover, this isachieved without requiring significant structural changes to the bolsteror side frame (a very critical factor in the railroad field).

With reference to the embodiment of FIGS. 13 16, roll control device 72Ais essentially the same as device 72 except for the characteristics ofits volute spring 73A that have been mentioned, which are achieved inthe form illustrated by employing a base disc 144A that is of reducedthickness as compared to the corresponding base disc 144 of device 72.As indicated in FIG. 15, base disc under surface 151A in the fonn shownis flat in nature for flush engagement with spring seat area 46 of theside frame but flattness is not required. The remaining parts of device72A are the same as device 72.

FIG. 12 is a graph illustrating the relation of volute spring trap freeheight, design free height and rap out height in devices arranged inaccordance with the invention. FIG. 12 plots rap out providing blowsagainst spring group height in inches. In a standard manufacturingprocedure that is employed to make volutes 73 and 73A, these volutes aresubjected to a series of ten hammer blows with a hammer suitable forthis purpose (such as a two pound machine hammer), and the rap outachieved for each blow, on the average, tends to follow the curve 160,which tends to go asymptotic at the volute design free height. IF thevolute is struck with a heavier blow, it may jump out in one jump todesign free height or perhaps somewhat more.

In accordance with this invention, the volute units are characterized bymaintaining their trap free height when the car is running empty againstthe action of what vibrations and impacts they will be subjected tounder normal operating conditions for the car. Such vibrations andimpacts will thus apply less force to the volute units than the unitforces needed to achieve rap out or jump out in the sense indicated byFIG. 12.

It will therefore be seen that this invention provides a method andapparatus for controlling roll of high capacity freight cars wherein thecar when empty has the soft resilient ride best suited to protect thecar structure when in route, considering the differences in center ofgravity and weight as compared to the fully loaded condition, whereasthe car when fully loaded is provided with full body roll control.Moreover, since the absorption potential of the roll control devices 72can be increased as desired up to approaching theoretical limits, due tothe freeing of the trap free height criteria from the empty car bolsterriding height level, the control provided by each volute unit 72 may besignificantly improved.

The invention is fully applicable to existing and new equipment and canbe readily applied to existing spring groups.

While it is intended that under normal conditions the roll absorbers ofthis invention will not be operating when the car is runr i'ng empty, itis contemplated that under some extremfi'condition the bolster when thecar is running empty may contact the roll absorber.

With regard to FIGS. 9 and 13, it is pointed out that the curves thereillustrated are theoretical for design purposes and do not show actualoperational curves.

The foregoing description and the drawings are given merely to explainand illustrate the invention and the invention is not to be limitedthereto, except insofar as the appended claims are so limited, sincethose skilled in the art who have the disclosure before them will beable to make modifications and variations therein without departing fromthe scope of the invention.

I claim:

1. In a railroad car truck for high capacity railroad cars with thetruck including a bolster supported from the truck side frames at eitherend of the bolster by a spring group interposed between the spring seatsof the respective bolster ends and the side frames supporting same,whereby said bolster has normal empty and loaded car riding heightsrelative to the respective side frames, the improvement wherein saidgroups each comprise:

a plurality of coil springs and at least one damping type roll controlvolute spring unit interposed between the bolster and side framessupporting same,

said coil springs engaging the spring seats of the bolster and sideframes, respectively, and being of sufficient strength to support thebolster at its empty car normal riding height whereby the bolsteroperates in an empty car riding height amplitude when the car moves overthe rails of track,

means exclusive of said volute units acting between the respectivebolster ends and the side frames supporting same for damping said coilsprings to con trol vertical movement of said bolster when operating insaid empty car normal ridingheight amplitude,

said coil springs having their strength limited such that when the carrides loaded, the bolster loaded car normal riding height amplitude isbelow and spaced vertically from the bolster empty car riding amplitude,

said units each comprising a roll control volute spring supported by theside frame beneath it and having a trap free height that is below thebolster empty car normal riding height amplitude and that is above thebolster loaded car normal riding height amplitude,

said volute springs when operative for roll control purposes providingsaid groups with a damping factor that is at least in the range of fromabout three to about four times the damping factor of said dampingmeans,

said volute springs each having an absorption potential that isindependent of the empty car riding height,

and including means for holding said volute springs seated within therespective groups when the bolster operates at a car riding height abovesaid trap free height,

whereby said coil springs providle ride characteristics for the car, tothe exclusion of said volute springs, that give spring cushioning actionsuitable for the car when the car rides empty, but said volute springsprovide full damping roll control when the car rides loaded.

2. The improvement set forth in claim 1 wherein:

said volute springs each have a negative helix angle and a reverse axialpitch.

3. The improvement set forth in claim 1 wherein:

said volute springs are each oriented to dispose outer coils of same atthe upper end thereof and the inner coils of same at the lower endthereof,

said volute springs each including coil spring means interposed betweensaid inner coils thereof and the bolster resilient maintaining therespective volute springs seated within the respective groups when thecar is empty, and comprising said holding means.

4. The improvement set forth in claim 1 wherein:

said volute springs have a load deflection relation such that part ofthe compression and release curves thereof are of the upwardly curvingtype.

5. The improvement set forth in claim 1 wherein:

said volute springs have a load deflection relation such that inproviding said damping roll control, said volute spring operate on asubstantially straight line load deflection basis.

* l i t

1. In a railroad car truck for high capacity railroad cars with thetruck including a bolster supported from the truck side frames at eitherend of the bolster by a spring group interposed between the spring seatsof the respective bolster ends and the side frames supporting same,whereby said bolster has normal empty and loaded car riding heightsrelative to the respective side frames, the improvement wherein saidgroups each comprise: a plurality of coil springs and at least onedamping type roll control volute spring unit interposed between thebolster and side frames supporting same, said coil springs engaging thespring seats of the bolster and side frames, respectively, and being ofsufficient strength to support the bolster at its empty car normalriding height whereby the bolster operates in an empty car riding heightamplitude when the car moves over the rails of track, means exclusive ofsaid volute units acting between the respective bolster ends and theside frames supporting same for damping said coil springs to controlvertical movement of said bolster when operating in said empty carnormal ridingheight amplitude, said coil springs having their strengthlimited such that when the car rides loaded, the bolster loaded carnormal riding height amplitude is below and spaced vertically from thebolster empty car riding amplitude, said units each comprising a rollcontrol volute spring supported by the side frame beneath it and havinga trap free height that is below the bolster empty car normal ridingheight amplitude and that is above the bolster loaded car normal ridingheight amplitude, said volute springs when operative for roll controlpurposes providing said groups with a damping factor that is at least inthe range of from about three to about four times the damping factor ofsaid damping means, said volute springs each having an absorptionpotential that is independent of the empty car riding height, andincluding means for holding said volute springs seated within therespective groups when the bolster operates at a car riding height abovesaid trap free height, whereby said coil springs provide ridecharacteristics for the car, to the exclusion of said volute springs,that give spring cushioning action suitable for the car when the carrides empty, but said volute springs provide full damping roll controlwhen the car rides loaded.
 2. The improvement set forth in claim 1wherein: said volute springs each have a negative helix angle and areverse axial pitch.
 3. The improvement set forth in claim 1 wherein:said volute springs are each oriented to dispose outer coils of same atthe upper end thereof and the inner coils of same at the lower endthereof, said volute springs each including coil spring means interposedbetween said inner coils thereof and the bolster resilient maintainingthe respective volute springs seated within the respective groups whenthe car is empty, and comprising said holding means.
 4. The improvementset forth in claim 1 wherein: said volute springs have a load deflectionrelation such that part of the compression and release curves thereofare of the upwardly curving type.
 5. The improvement set forth in claim1 wherein: said volute springs have a load deflection relation such thatin providing said damping roll control, said volute spring operate on asubstantially straight line load deflection basis.